/* ===== reset ===== */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;text-size-adjust:100%;scroll-behavior:smooth;scroll-padding-top:80px}
body{margin:0;min-height:100vh}
h1,h2,h3,h4,h5,h6,p,figure,blockquote,dl,dd{margin:0}
ul,ol{margin:0;padding:0;list-style:none}
img,svg{display:block;max-width:100%}
button,input,select,textarea{font:inherit;color:inherit}
table{border-collapse:collapse;width:100%}

/* ===== tokens ===== */
:root{
  color-scheme:light;
  --blue:#1E6BFF;--blue-deep:#0B3FA8;--cyan:#00E5C3;--orange:#FF6B2C;
  --charcoal:#0E1116;--rock:#232A33;--paper:#F7F8FA;--mineral:#EDE8DE;--moss:#4A6B57;
  --bg:var(--paper);--bg-alt:var(--mineral);--surface:#FFFFFF;
  --text:#12161C;--heading:#12161C;--text-soft:#5A6472;
  --line:rgba(18,22,28,.16);--line-soft:rgba(18,22,28,.05);
  --accent-text:#1E6BFF;
  --rail-bg:#0E1116;--rail-text:#F7F8FA;--rail-soft:#9AA3B0;
  --rail-w:96px;
  --mono:"JetBrains Mono",ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  --sans:"HarmonyOS Sans SC","Source Han Sans SC","Noto Sans SC","PingFang SC","Microsoft YaHei",system-ui,-apple-system,sans-serif;
  --ease:cubic-bezier(.2,.7,.3,1);
}
@media (prefers-color-scheme:dark){
  :root:not([data-theme="light"]){
    color-scheme:dark;
    --bg:#0E1116;--bg-alt:#151B23;--surface:#232A33;
    --text:#E6E9EE;--heading:#FFFFFF;--text-soft:#9AA3B0;
    --line:rgba(255,255,255,.15);--line-soft:rgba(255,255,255,.05);
    --accent-text:#6FA2FF;
    --rail-bg:#0B0F14;--rail-text:#F7F8FA;--rail-soft:#9AA3B0;
  }
}
:root[data-theme="dark"]{
  color-scheme:dark;
  --bg:#0E1116;--bg-alt:#151B23;--surface:#232A33;
  --text:#E6E9EE;--heading:#FFFFFF;--text-soft:#9AA3B0;
  --line:rgba(255,255,255,.15);--line-soft:rgba(255,255,255,.05);
  --accent-text:#6FA2FF;
  --rail-bg:#0B0F14;--rail-text:#F7F8FA;--rail-soft:#9AA3B0;
}

/* ===== base ===== */
body{
  font-family:var(--sans);font-size:17px;line-height:1.7;
  color:var(--text);background-color:var(--bg);
  background-image:
    linear-gradient(to right,var(--line-soft) 1px,transparent 1px),
    linear-gradient(to bottom,var(--line-soft) 1px,transparent 1px);
  background-size:72px 72px;
  -webkit-font-smoothing:antialiased;
  transition:background-color .3s var(--ease),color .3s var(--ease);
}
@media (min-width:1024px){body{padding-left:var(--rail-w)}}
@media (max-width:1023px){body{padding-top:56px}}
h1,h2,h3,h4{font-family:var(--sans);font-weight:800;line-height:1.15;letter-spacing:-.015em;color:var(--heading);margin:0 0 .5em}
h1{font-size:clamp(34px,4.6vw,64px)}
h2{font-size:clamp(24px,2.6vw,34px)}
h3{font-size:20px}
h4{font-size:17px}
p{margin:0 0 1em}
a{color:var(--accent-text);text-decoration:none}
a:hover{color:var(--blue)}
strong{font-weight:800;color:var(--heading)}
::selection{background:var(--cyan);color:#04120F}
:focus-visible{outline:2px solid var(--cyan);outline-offset:3px}

/* ===== skip link ===== */
.skip-link{
  position:fixed;top:10px;left:50%;z-index:200;
  transform:translate(-50%,-160%);
  padding:10px 18px;border-radius:2px;
  background:var(--cyan);color:#04120F;font-weight:800;font-size:14px;
  text-decoration:none;transition:transform .2s var(--ease);
}
.skip-link:focus,.skip-link:focus-visible{transform:translate(-50%,0);outline:2px solid #04120F;outline-offset:2px}

/* ===== header shell ===== */
.site-header{position:fixed;top:0;left:0;bottom:0;width:var(--rail-w);z-index:90}
.rail-progress{
  position:absolute;top:0;left:0;width:3px;height:100%;
  background:linear-gradient(180deg,var(--cyan),var(--blue-deep));
  transform:scaleY(var(--progress,0));transform-origin:top center;
  transition:transform .12s linear;pointer-events:none;z-index:2;
}
.rail{
  position:relative;z-index:1;display:flex;flex-direction:column;align-items:stretch;
  height:100%;padding:16px 9px 14px;gap:14px;
  background:var(--rail-bg);color:var(--rail-text);
  border-right:1px solid rgba(255,255,255,.10);
  transition:background-color .3s var(--ease);
}
.site-header::after{
  content:"";position:absolute;top:0;right:0;bottom:0;width:4px;
  background:repeating-linear-gradient(180deg,rgba(255,255,255,.24) 0 1px,transparent 1px 24px);
  opacity:.55;pointer-events:none;z-index:2;
}

/* brand */
.rail__brand{display:flex;flex-direction:column;align-items:center;gap:8px;text-align:center}
.rail__logo{display:flex;flex-direction:column;align-items:center;gap:7px;text-decoration:none;color:var(--rail-text)}
.rail__logo-mark{
  display:grid;place-items:center;width:38px;height:38px;
  font-family:var(--mono);font-size:13px;font-weight:700;letter-spacing:.04em;
  color:#04120F;background:linear-gradient(150deg,var(--cyan) 0%,var(--blue) 100%);
  clip-path:polygon(0 0,100% 0,100% 68%,68% 100%,0 100%);
}
.rail__logo-text{writing-mode:vertical-rl;font-size:12px;font-weight:800;letter-spacing:.22em;line-height:1}
.rail__badge{
  display:inline-flex;align-items:center;justify-content:center;gap:4px;
  padding:3px 5px;border:1px solid rgba(0,229,195,.45);border-radius:2px;
  font-family:var(--mono);font-size:9px;line-height:1.4;letter-spacing:.02em;color:var(--cyan);
  text-align:center;
}
.rail__badge-dot{width:5px;height:5px;border-radius:50%;background:var(--cyan);box-shadow:0 0 0 2px rgba(0,229,195,.22);flex:none}

/* nav toggle */
.nav-toggle{display:none;align-items:center;gap:7px;padding:8px 12px;border-radius:2px;
  background:rgba(255,255,255,.06);border:1px solid rgba(255,255,255,.22);
  color:var(--rail-text);font-size:12px;font-weight:700;cursor:pointer;
  transition:background-color .2s var(--ease),border-color .2s var(--ease)}
.nav-toggle:hover{background:rgba(0,229,195,.14);border-color:var(--cyan)}
.nav-toggle__bars{display:inline-flex;flex-direction:column;gap:3px;width:16px}
.nav-toggle__bars span{display:block;height:2px;background:var(--cyan);transition:transform .22s var(--ease),opacity .22s var(--ease)}
.nav-toggle__label{font-size:12px;letter-spacing:.06em}
.site-header[data-open] .nav-toggle__bars span:nth-child(1){transform:translateY(5px) rotate(45deg)}
.site-header[data-open] .nav-toggle__bars span:nth-child(2){opacity:0}
.site-header[data-open] .nav-toggle__bars span:nth-child(3){transform:translateY(-5px) rotate(-45deg)}

/* vertical nav */
.site-nav{display:flex;flex-direction:column}
.site-nav__list{display:flex;flex-direction:column;gap:2px}
.site-nav__item{list-style:none}
.site-nav__link{
  position:relative;display:flex;flex-direction:column;align-items:center;gap:2px;
  padding:8px 6px;border:1px solid transparent;border-radius:2px;
  text-decoration:none;color:var(--rail-soft);
  transition:color .2s var(--ease),background-color .2s var(--ease),border-color .2s var(--ease);
}
.site-nav__num{font-family:var(--mono);font-size:9px;letter-spacing:.14em;color:rgba(255,255,255,.42);transition:color .2s var(--ease)}
.site-nav__label{font-size:12px;font-weight:700;line-height:1.2;text-align:center}
.site-nav__link:hover{color:#fff;background:rgba(255,255,255,.07)}
.site-nav__link:hover .site-nav__num{color:var(--cyan)}
.site-nav__link[aria-current="page"]{color:#fff;background:rgba(30,107,255,.16);border-color:rgba(30,107,255,.55)}
.site-nav__link[aria-current="page"] .site-nav__num{color:var(--cyan)}
.site-nav__mark{
  position:absolute;right:-9px;top:50%;width:2px;height:18px;background:var(--cyan);
  transform:translateY(-50%) scaleY(0);transform-origin:center;opacity:.9;
  transition:transform .26s var(--ease),opacity .26s var(--ease);
}
.site-nav__link[aria-current="page"] .site-nav__mark{transform:translateY(-50%) scaleY(1);opacity:1}
.site-nav__link--guide .site-nav__mark{transform:translateY(-50%) scaleY(.45);opacity:.6}
.site-nav__link--guide[aria-current="page"] .site-nav__mark{transform:translateY(-50%) scaleY(1);opacity:1}

/* rail foot */
.rail__foot{margin-top:auto;display:flex;flex-direction:column;gap:8px;align-items:stretch}
.rail__actions{display:flex;flex-direction:column;gap:6px}
.rail__meta{margin:0;font-family:var(--mono);font-size:9px;letter-spacing:.08em;color:rgba(255,255,255,.4);text-align:center}

/* buttons */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:6px;
  padding:11px 18px;border:1px solid transparent;border-radius:2px;
  font-family:var(--sans);font-size:14px;font-weight:700;line-height:1.2;
  text-align:center;text-decoration:none;cursor:pointer;
  transition:background-color .2s var(--ease),color .2s var(--ease),border-color .2s var(--ease),transform .2s var(--ease);
}
.btn--primary{background:var(--blue);color:#fff;box-shadow:0 0 0 1px rgba(30,107,255,.35),0 10px 24px -14px rgba(30,107,255,.95)}
.btn--primary:hover{background:var(--blue-deep);color:#fff;transform:translateY(-1px)}
.btn--ghost{background:transparent;color:var(--cyan);border-color:rgba(0,229,195,.5)}
.btn--ghost:hover{background:rgba(0,229,195,.12);border-color:var(--cyan);color:var(--cyan)}
.btn--rail{font-size:11px;line-height:1.35;padding:8px 4px;letter-spacing:.02em;word-break:break-word}

/* theme toggle */
.theme-toggle{
  display:flex;align-items:center;justify-content:center;gap:5px;width:100%;
  padding:7px 4px;border-radius:2px;
  background:rgba(255,255,255,.05);border:1px solid rgba(255,255,255,.18);
  color:var(--rail-text);font-family:var(--sans);font-size:11px;font-weight:600;cursor:pointer;
  transition:background-color .2s var(--ease),border-color .2s var(--ease);
}
.theme-toggle:hover{background:rgba(0,229,195,.14);border-color:var(--cyan)}
.theme-toggle__icon{width:11px;height:11px;border-radius:50%;border:1px solid var(--cyan);background:linear-gradient(90deg,var(--cyan) 0 50%,transparent 50% 100%);flex:none}
.theme-toggle[aria-pressed="true"] .theme-toggle__icon{background:var(--cyan)}
.theme-toggle__text{white-space:nowrap}

/* ===== footer ===== */
.site-footer{
  --f-bg:#0B0F14;--f-text:#E6E9EE;--f-soft:#9AA3B0;--f-line:rgba(255,255,255,.14);
  position:relative;margin-top:clamp(56px,8vw,96px);
  background:var(--f-bg);color:var(--f-text);
  border-top:1px solid var(--f-line);
}
.site-footer::before{
  content:"";position:absolute;top:0;left:0;right:0;height:2px;
  background:linear-gradient(90deg,var(--blue) 0 96px,var(--cyan) 96px 132px,rgba(255,255,255,.14) 132px 100%);
}
.footer-frame{max-width:1240px;margin:0 auto;padding:clamp(48px,6vw,72px) clamp(20px,4vw,48px) 28px}
.footer-grid{display:grid;grid-template-columns:minmax(0,1.5fr) repeat(3,minmax(0,.75fr));gap:clamp(24px,3vw,40px)}
.footer-brand__logo{display:inline-block;font-size:20px;font-weight:900;letter-spacing:.02em;color:#fff;text-decoration:none;padding-bottom:4px;border-bottom:2px solid var(--cyan)}
.footer-brand__logo:hover{color:var(--cyan)}
.footer-brand__tag{margin:14px 0 0;font-family:var(--mono);font-size:11px;letter-spacing:.18em;color:var(--cyan)}
.footer-brand__note{margin:14px 0 0;max-width:36ch;font-size:13px;line-height:1.75;color:var(--f-soft)}
.footer-brand__sig{margin:16px 0 0;font-family:var(--mono);font-size:11px;letter-spacing:.1em;color:rgba(255,255,255,.5)}
.footer-col__title{margin:0 0 14px;font-size:12px;font-weight:800;letter-spacing:.22em;color:var(--f-soft);text-transform:uppercase}
.footer-col__list{display:flex;flex-direction:column;gap:9px}
.footer-col__link{display:inline-block;padding-bottom:1px;font-size:14px;color:var(--f-text);text-decoration:none;border-bottom:1px solid transparent;transition:color .2s var(--ease),border-color .2s var(--ease)}
.footer-col__link:hover{color:var(--cyan);border-color:var(--cyan)}
.footer-contact{display:flex;flex-wrap:wrap;gap:10px 28px;margin-top:clamp(28px,4vw,44px);padding-top:22px;border-top:1px solid var(--f-line);font-size:13px;color:var(--f-soft)}
.footer-contact__item{display:inline-flex;align-items:baseline;gap:8px;margin:0}
.footer-contact__key{font-family:var(--mono);font-size:10px;letter-spacing:.14em;color:var(--cyan)}
.footer-legal{display:flex;flex-wrap:wrap;align-items:center;gap:10px 24px;margin-top:22px;padding-top:16px;border-top:1px solid var(--f-line);font-family:var(--mono);font-size:11px;letter-spacing:.04em;color:rgba(255,255,255,.52)}
.footer-legal__copy,.footer-legal__icp{margin:0}
.footer-legal__links{display:flex;flex-wrap:wrap;gap:16px;margin-left:auto}
.footer-legal__link{color:rgba(255,255,255,.72);text-decoration:none;border-bottom:1px solid rgba(255,255,255,.2);transition:color .2s var(--ease),border-color .2s var(--ease)}
.footer-legal__link:hover{color:var(--cyan);border-color:var(--cyan)}

/* back to top */
.to-top{
  position:fixed;right:clamp(14px,3vw,28px);bottom:clamp(14px,3vw,28px);z-index:95;
  display:grid;place-items:center;width:46px;height:46px;
  border:1px solid rgba(255,255,255,.24);border-radius:2px;
  background:var(--blue);color:#fff;font-size:18px;line-height:1;cursor:pointer;
  opacity:0;pointer-events:none;transform:translateY(10px);
  transition:opacity .22s var(--ease),transform .22s var(--ease),background-color .2s var(--ease);
}
.to-top[data-visible]{opacity:1;pointer-events:auto;transform:none}
.to-top:hover{background:var(--blue-deep)}

/* ===== shared content utilities ===== */
.container{width:100%;max-width:1240px;margin-inline:auto;padding-inline:clamp(20px,4vw,48px)}
.section{padding-block:clamp(56px,8vw,96px)}
.prose{max-width:66ch;font-size:17px;line-height:1.75;color:var(--text)}
.prose p{margin:0 0 1.1em}
.prose h2{font-size:clamp(22px,2.2vw,30px);margin:1.6em 0 .6em}
.prose h3{font-size:19px;margin:1.4em 0 .5em}
.prose ul,.prose ol{margin:0 0 1.2em;padding:0;list-style:none}
.prose li{position:relative;padding-left:22px;margin-bottom:.5em}
.prose li::before{content:"";position:absolute;left:0;top:.74em;width:10px;height:1px;background:var(--cyan)}
.prose ol{counter-reset:prose}
.prose ol li{counter-increment:prose;padding-left:34px}
.prose ol li::before{content:counter(prose,decimal-leading-zero);top:.32em;left:0;width:auto;height:auto;background:none;font-family:var(--mono);font-size:12px;color:var(--blue)}
.prose blockquote{margin:0 0 1.2em;padding:14px 20px;border-left:2px solid var(--cyan);background:var(--bg-alt);font-size:16px;color:var(--text-soft)}

.chapter-mark{display:flex;align-items:center;gap:12px;padding-bottom:10px;margin-bottom:22px;border-bottom:1px solid var(--line)}
.chapter-mark__num{font-family:var(--mono);font-size:12px;letter-spacing:.16em;color:var(--blue)}
.chapter-mark__label{font-size:12px;font-weight:800;letter-spacing:.22em;color:var(--text-soft);text-transform:uppercase}

.breadcrumb{font-family:var(--mono);font-size:12px;letter-spacing:.06em;color:var(--text-soft)}
.breadcrumb__list{display:flex;flex-wrap:wrap;gap:8px;list-style:none;margin:0;padding:0}
.breadcrumb__item{display:flex;align-items:center;gap:8px}
.breadcrumb__link{color:inherit;text-decoration:none;border-bottom:1px solid transparent;transition:color .2s var(--ease),border-color .2s var(--ease)}
.breadcrumb__link:hover{color:var(--blue);border-color:var(--blue)}
.breadcrumb__sep{color:var(--fog,#9AA3B0);opacity:.7}

.tag{display:inline-flex;align-items:center;gap:6px;padding:4px 9px;border:1px solid var(--line);border-radius:2px;background:var(--surface);color:var(--text-soft);font-family:var(--mono);font-size:11px;letter-spacing:.1em}
.tag--cyan{background:var(--cyan);border-color:var(--cyan);color:#062B26}
.tag--orange{background:var(--orange);border-color:var(--orange);color:#2A0D02}
.tag--moss{background:var(--moss);border-color:var(--moss);color:#F2F6F2}

.figure-frame{position:relative;border:1px solid var(--line);background:var(--surface)}
.figure-frame__media{position:relative;overflow:hidden;background:var(--bg-alt)}
.figure-frame__media img{display:block;width:100%;height:100%;object-fit:cover}
.figure-frame__cap{margin:0;padding:9px 12px;border-top:1px solid var(--line);background:var(--surface);font-family:var(--mono);font-size:11px;letter-spacing:.06em;color:var(--text-soft)}
.figure-frame--tint .figure-frame__media::after{content:"";position:absolute;inset:0;pointer-events:none;background:linear-gradient(140deg,rgba(30,107,255,.28),rgba(0,229,195,.16) 55%,rgba(255,107,44,.22));mix-blend-mode:screen}
.ratio-16x9{aspect-ratio:16/9}
.ratio-4x3{aspect-ratio:4/3}
.ratio-1x1{aspect-ratio:1/1}
.ratio-3x4{aspect-ratio:3/4}

.u-mono{font-family:var(--mono);font-size:14px;letter-spacing:.04em}

[data-reveal]{opacity:0;transform:translateY(12px);transition:opacity .5s var(--ease),transform .5s var(--ease)}
.is-visible{opacity:1;transform:none}

/* ===== responsive: header -> top sticky bar ===== */
@media (max-width:1023px){
  .site-header{top:0;left:0;right:0;bottom:auto;width:100%}
  .site-header::after{
    top:auto;bottom:0;left:0;right:0;width:auto;height:3px;
    background:repeating-linear-gradient(90deg,rgba(0,229,195,.55) 0 2px,transparent 2px 18px);
    opacity:.6;
  }
  .rail-progress{
    top:auto;bottom:0;left:0;width:100%;height:3px;
    transform:scaleX(var(--progress,0));transform-origin:left center;
    background:linear-gradient(90deg,var(--cyan),var(--blue-deep));
  }
  .rail{
    flex-direction:row;flex-wrap:wrap;align-items:center;
    height:auto;min-height:56px;max-height:100vh;
    padding:0 12px;gap:0 10px;overflow-y:auto;
    border-right:0;border-bottom:1px solid rgba(255,255,255,.12);
  }
  .rail__brand{order:1;flex:1 1 auto;flex-direction:row;align-items:center;gap:8px;padding:10px 0}
  .rail__logo{flex-direction:row;gap:8px}
  .rail__logo-mark{width:26px;height:26px;font-size:10px}
  .rail__logo-text{writing-mode:horizontal-tb;font-size:13px;letter-spacing:.14em}
  .rail__badge{display:none}
  .nav-toggle{order:2;display:inline-flex}
  .site-nav{order:3;flex:1 0 100%;width:100%;display:none;padding:4px 0 10px}
  .site-nav[data-open]{display:block}
  .site-nav__list{flex-direction:row;gap:8px;overflow-x:auto;padding-bottom:6px;-webkit-overflow-scrolling:touch}
  .site-nav__item{flex:0 0 auto}
  .site-nav__link{flex-direction:row;align-items:center;gap:7px;padding:8px 12px;border-color:rgba(255,255,255,.16);background:rgba(255,255,255,.04)}
  .site-nav__num{font-size:10px}
  .site-nav__label{font-size:13px;white-space:nowrap}
  .site-nav__mark{display:none}
  .rail__foot{order:4;flex:1 0 100%;width:100%;display:none;margin-top:0;flex-direction:row;flex-wrap:wrap;align-items:center;gap:8px;padding-bottom:12px}
  .rail__actions{flex-direction:row;flex:1 1 auto;gap:8px}
  .btn--rail{font-size:13px;padding:9px 14px}
  .theme-toggle{width:auto;padding:9px 12px;font-size:12px}
  .rail__meta{display:none}
  .site-header[data-open] .site-nav{display:block}
  .site-header[data-open] .rail__foot{display:flex}
}
@media (min-width:1024px) and (max-height:760px){
  .rail{gap:8px;padding-top:10px}
  .rail__logo-text{display:none}
  .rail__badge{display:none}
  .site-nav__link{padding:7px 6px}
}

/* ===== responsive: footer ===== */
@media (max-width:900px){
  .footer-grid{grid-template-columns:repeat(2,minmax(0,1fr))}
  .footer-brand{grid-column:1 / -1}
}
@media (max-width:560px){
  .footer-grid{grid-template-columns:1fr}
  .footer-legal__links{margin-left:0}
  .footer-contact{flex-direction:column;gap:8px}
}

/* ===== motion ===== */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation-duration:.001ms !important;animation-iteration-count:1 !important;transition-duration:.001ms !important;scroll-behavior:auto !important}
  [data-reveal]{opacity:1 !important;transform:none !important}
  .rail-progress{transition:none}
}